Quantum Mechanics and Why You Should Care

1 year, 11 months ago

I’m going to make this understandable for everyone without going into the deeper physics, because this is stuff everyone should know and be able to appreciate about the universe.

When things get really small, a phenomenon called superposition occurs. All you need to know about this thing called superposition is that an object (you, an atom, an electron) can’t be described neatly with precise values. Instead, all the quantities something can have, be it energy, position, velocity, etc, take on many values simultaneously. The way to think about this is to imagine the position of a particle, let’s use a proton, as a cloud. Closer to the middle of the cloud is really dark, and as you look further away from the center (in any direction), it grows less dense. The cloud never really entirely disappears, but there’s still a finite amount of cloud out there (It’s a weird idea so just go with it if you need to). The cloud is a probability map of all the positions the proton is currently in. It’s easy to see if we zoom out how we can mistake the cloud for a point. But we’ve looked closer and careful experimentation has revealed this startling fact about nature.

Now this is where it gets good. When we ask the proton where it is, it gives us a single value – NOT a cloud. The most popular interpretation of this event is that during the act of measurement, we “collapse” the cloud and turn it into a point. The fancy name for this is wavefunction collapse. BUT – there’s a counter-hypothesis, which says that when we interact with the proton and ask where it is, instead of the proton’s cloud collapsing to a point, we expand from a point to a cloud ourselves! In other words, there’s a you for every corresponding position in the cloud the proton could have had. You can see how the wavefunction collapse people conclude that it’s the proton’s cloud that has collapsed to a point, rather than your point expanding to a cloud. It’s the problem of consciousness and experience – we can only experience one outcome, which makes it impossible to tell what’s actually happening.

But let’s talk about why this is important for you. We said proton’s can be a cloud. And so can you, once you interact with the proton. Well, it turns out the entire universe is a cloud! There’s no reason to suppose you can’t simply apply the previous situation to more complex situations. Consider the cloud-you interacting with your friend and sharing the position you found the proton at. Your friend becomes a cloud, and so it goes on! The universe is a cloud, and a widely variable cloud at that. Interactions between particles happen so frequently it’s reasonable to suppose that other portions of the universe’s cloud can be entirely different – you may not exist at all! When cloud’s interact with other clouds and become larger, the variability magnifies until this phenomenon called superposition affects things even at our macro-level of life.

And that’s why you should care about quantum mechanics. It’s not just about the quantum level of things, it operates at our level too. You simply live at a single point in the Universe’s cloud. Your reality is not the only reality.

Note to people who actually know quantum mechanics:
My slightly bastardized version above is about the debate between the Copenhagen Interpretation and the Many Worlds Interpretation of quantum mechanics. I believe that the Copenhagen interpretation has no logical basis, that it introduces unnecessary phenomena (Occam’s Razer keep it simple amirite?), and that we can explain the appearance of wavefunction collapse by simply appealing to the principles we already have at our disposal. I subsitute the concept “cloud” for “wavefunction” to make it more accessible and commit the crime of suggesting there are alternate universes or realities when in fact it’s not so much that as it is one universe in many states simultaneously. Let me know what you think

December 30, 2012 at 12:41 am

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Profile photo of littlefoot littlefoot (@littlefoot) 1 year, 11 months ago ago

Bah I love these theories, so so much. Thanks!

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Profile photo of  Anonymous (@) 1 year, 11 months ago ago

There are some obvious problems to keep in mind when considering the Copenhagen interpretation:

1) Its application to macroscopic objects (lol)
2) Why exactly conscious observers are so “special”

In other words, I’m not the biggest fan.

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Profile photo of Alex Alex M (@alexishungry) 1 year, 11 months ago ago

@tayrex, Awesome post. As much as quantum mechanics interests me, I agree with @dalniente, I never really liked the Copenhagen interpretation either.
What if we go really macroscopic? Who is the observer of the universe as a whole?

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Profile photo of Filip Filip M (@filipek) 1 year, 11 months ago ago

@tayrex, Thanks for sharing this! I love the subject of Quantum Physics!

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Profile photo of Daniel Daniel (@qwuakeup) 1 year, 11 months ago ago

We are the observer of the universe as a whole. We are just awareness – observation.

Everything that is outside of us is a reflection of our inner being – our core beliefs.

All we are is consciousness – and everything else is a projection of consciousness, so therefore everything is consciousness.

So we can say that we are everything , and everything is us.

This can’t be intellectual understood by logic or science. It can only be experienced. No one can prove it to you, only you can experience it yourself. It can be experienced through meditation – moving your awareness from the mind and going deep into being.

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Profile photo of stonerphysicist stonerphysicist (@tayrex) 1 year, 11 months ago ago

@dalniente, @alexishungry, I have a question for you guys. You both said it yourselves, and it’s often cited in quantum mechanics textbooks, that conscious observers change the way things work by collapsing the wavefunction. The thing is, there’s no reason to suppose conscious observers behave any different from a particle like a proton. The point of my original post is to suggest that we enter into entanglement with particles through our interactions with them. Thus, it’s not so much that we change the universe by observing it, but that our observation means that we will consciously experience only one outcome, when in fact all outcomes happen and the many you’s out there experience them all.

This brings up a second point which is my main objection to theories that overemphasize the identity of a person (like spirituality): Since the natural extension of superposition to the macro-level suggests that the universal wavefunction varies dramatically, rather than narrowly, brought on by the magnitude of particle interactions, it makes sense to believe that your identity is only one of many. For example, maybe in 40% of possible universes you exist, in 60% you don’t. And within those 40% you experience only a single outcome. So when you get really deep into spiritual discussions and whatnot, just remember that you are only one of many, and an overly self-absorbed one at that. (As an afterthought, I can see a type of spirituality that acknowledges this still being meaningful)

Now, we’ll never really know if we exist in superposition because of the problem of consciousness and single-experience, but I think it could be possible to one-day perform a macroscopic investigation of quantum mechanics through some ingenious experiment that reveals we do in fact exist in superposition. They’ve done it with buckyballs, currents in a wire, why not us?

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Profile photo of Alex Alex M (@alexishungry) 1 year, 11 months ago ago

@tayrex, I understand what you’re saying, but even if we ourselves collapse our own “wave function” into several different “us”es that observe the particle at different points, there is no way to actually know for sure if that’s what really happens, because we’re only ONE of the “us”es. It’s hard to put what I’m thinking into words. But that’s why I’m a little skeptical about it. Maybe I just don’t understand it as well as you do. Like you were saying, if they’re able to confirm it in an experiment, I’d be excited, but until then, I still feel iffy about it.

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Profile photo of  Anonymous (@) 1 year, 11 months ago ago

@alexishungry, your avatar makes me all warm and fuzzy inside. :)

@qwuakeup, could you be any more vague?

@tayrex, as for the many-worlds interpretation, there is the issue that gravity must behave non-linearly when quantized. I focused on your criticisms of the Copenhagen interpretation; you seem to have at least a decent understanding of both (and the inadequacies of interpretations in general). .

At the macroscopic level, particles observe one another. To anyone reading who may not understand, that causes their wave functions to collapse. The microscopic level is really only “spooky” because we’re not accustomed to it. I haven’t met many well-educated people who take Schrodinger’s thought experiment too seriously. Also, despite the obvious challenges it poses, it could be theoretically possible to entangle a system that large.

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Profile photo of josephm josephm (@josephm) 1 year, 11 months ago ago

@tayrex, Tldr. yes i agree.

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Profile photo of Daniel Daniel (@qwuakeup) 1 year, 11 months ago ago

@dalniente, Yes. Meditate

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Profile photo of Sasho Stoyanov Anonymous (@) 1 year, 11 months ago ago

“But let’s talk about why this is important for you.” – You really didn’t talk about why this is important for me or why I should care. Sorry.

“The universe is a cloud, and a widely variable cloud at that. Interactions between particles happen so frequently it’s reasonable to suppose that other portions of the universe’s cloud can be entirely different – you may not exist at all!” – ?

“And that’s why you should care about quantum mechanics. It’s not just about the quantum level of things, it operates at our level too. You simply live at a single point in the Universe’s cloud. Your reality is not the only reality.”

“could you be any more vague?”

“Yes.”

This is making me care less to be honest. :)

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Profile photo of Alex Alex M (@alexishungry) 1 year, 11 months ago ago

@qwuakeup, “This can’t be intellectual[ly] understood by logic or science” Serotonin? Dopamine? Phenylethylamine?

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Profile photo of Mr. Arbiter Mr. Arbiter (@snaysler) 1 year, 11 months ago ago

@beyond, “you may not exist at all!” – reason why it’s important to you

@tayrex, Nice post! Kind of sounds like it was inspired by the concepts of my piece on the post we met on, except it uses more science to back it up and make it more credible. It’s strange and almost humorous how the universe seems to be too lazy to be definite unless it really has to, by being under scrutiny. I really wish I had proper knowledge of these matters, but I won’t be taking a quantum physics course until the next academic year; I’m kinda jealous

btw- I’m starting to put my thoughts on paper for that consciousness thing :)

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Profile photo of Sasho Stoyanov Anonymous (@) 1 year, 11 months ago ago

@snaysler, It’s thought provoking, but nowhere near making sense, thanks.

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Profile photo of  Anonymous (@) 1 year, 11 months ago ago

@snaysler, I’m curious to know how far your math education has come along. There are courses you could try online if you have the time. Lately I’ve been focusing on differential geometry and fun applications of topology, which have also improved my understanding of QM. Although I do appreciate the popularization of science, that has also led to vague “philosophical” interpretations, reliance on layman’s terms, etc.

You may be interested in deterministic interpretations of quantum mechanics. Some over-simplify the issue by saying modern physics has completely debunked determinism.

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Profile photo of stonerphysicist stonerphysicist (@tayrex) 1 year, 11 months ago ago

@dalniente, I did some follow-up on “As for the many-worlds interpretation, there is the issue that gravity must behave non-linearly when quantized” and just found out a whole bunch of stuff I never knew. So apparently the Schrodinger equation is just an approximation that breaks down at one end of the spectrum when the true non-linearity reveals itself and becomes non-negligible. Did some reading about the non-linear form of the equation – which is hypothetically the true description of reality, whereas the linear form is just nicer to work with. Very interesting stuff.

The thing I don’t understand is how the non-linearity breaks the Many Worlds Interpretation. I read multiple sources that describe the Many Worlds Interpretation as listing linearity as an assumption, but I’m having a hard time grasping why that is. Correct me if I’m wrong, but doesn’t the assumption lie at the level of Quantum Mechanics itself, rather than at the level of an interpretation? The interpretation simply states that all outcomes do in fact happen rather than a single outcome. How does this require linearity? If it’s the principles of quantum mechanics that require linearity, and since we found non-linearity, those must be wrong, and thus corresponding interpretations are wrong, then I believe it, but I don’t see it the other way. I’m just questioning because I’m confused not because I think the world is wrong about this or anything. Thanks!

Also I want to add that I think determinism still stands strong (mostly) despite the findings of Quantum Mechanics

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Profile photo of  Anonymous (@) 1 year, 11 months ago ago

@tayrex, there is a problem when people take the many-worlds interpretation too literally. Although it has some appeal, linearity is just assumed, and any kind of collapse postulate is rejected. Max Tegmark, a many-worlds proponent that I do admire, and others do not seem to be very familiar with quantum gravity. Speaking of Tegmark, I’ve posted a paper of his on “quantum decoherence in brain processes” a few times on here when quantum consciousness (silliness) was brought up.

http://arxiv.org/abs/quant-ph/9907009

http://space.mit.edu/home/tegmark/

Back on topic…

Work has shown that all gravity is non-linear when quantized. The linear formulation of quantum mechanics depends on a classical spacetime manifold. There are no classical fields in the universe; when considering that, the classical spacetime manifold pretty much bursts into flames. (figuratively) Quantum gravity is non-linear because classical spacetime breaks down at the Planck scale.

That being said, it’s interesting to see how MWI has gained popularity. For example, I also frequent a forum called Less Wrong. I have issues with some of the things in the link below, but you may enjoy it. Overall the site is fun to read.

http://lesswrong.com/lw/r5/the_quantum_physics_sequence/

http://plato.stanford.edu/entries/spacetime-holearg/

http://arxiv.org/abs/0705.2357

arxiv.org/find/grp_physics/1/au:+ashtekar/0/1/0/all/0/1

Edit: do you happen to enjoy the work of Spinoza?

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Profile photo of Tine Tine (@tine) 1 year, 11 months ago ago

@tayrex,

hrmmm, i like what you posted, thank you, very informative, i also understand the need to theorize, as theories are abstract trains of thought that are designed to be molded and built upon, but i wonder how much proof can be demonstrated through quantum theory?

can you enlighten me a little about how the quantum theory is used in a practical way? what i mean is, can you give me some tangible cause/effects that are measurable and observable, when considered from the theory’s context?

here is my concern, humans are limited to what they experience and know, their perspective, most humans only have small working mental models of the world, even highly intelligent ones, and most humans perspectives are clouded by emotion, a false reality,

so when i hear a theory that explains the cosmos, i am concerned, every one of those individuals who champion it are limited to the perspective of this world, all their ideas, all the ideas they built upon throughout history, are also limited to this world, the cause / effect that is observable here,

the universe is unknown, completely unknown, and completely different,

so, can you give me something that takes this theory out of the realm of complex thought and bears some tangibility? i realize your post was not about the universe, this is just the main way i’ve seen quantum theory used

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Profile photo of stonerphysicist stonerphysicist (@tayrex) 1 year, 11 months ago ago

@tine, of course I’d love to

The two questions you seem to be asking are:
1. How can we reason about the rest of the universe simply from our experience here on Earth?
2. What empirical proof is there that Quantum theory is correct?

Here are your answers my sir:
1. We can’t. There’s this belief that physicists have, which I’m going to call space equality, which says that every point in space is subject to the same laws as every other point in space. Now, this is an assumption. There is no logical basis for this fact. It’s similar to the idea of induction, the idea that if something has happened n times (where n is very large), it will happen n+1 times. Note this is separate from mathematical induction, which is deductive, because induction as method of argument discovery about the world has no logical basis. It is inductive; it doesn’t prove things for certain. But let’s examine whether we have adequately explored enough space such that n is large enough to say we have a strong argument…I think everyone would agree the answer is no. We orbit the sun – we have sent very few things to other places – the universe is huge – and therefore we have explored almost 0% of it. BUT, there is one method we have for collecting evidence about the laws of the universe at other points in space. We can analyze phenomenon on Earth and apply them to things we see elsewhere in space. If our predictions line up with reality, then it’s reasonable to guess that the rest of space obeys the same laws of physics. But we still don’t escape the problem of induction, and thus the answer to your question is that we don’t know that the universe is uniform. We think it’s so, but we’re not sure. But that’s all science, isn’t it? To say something absolutely is the thing of religion and non science. Here’s some Richard Feynman for you:
“We absolutely must leave room for doubt or there is no progress and there is no learning. There is no learning without having to pose a question. And a question requires doubt. People search for certainty. But there is no certainty. People are terrified – how can you live and not know? It is not odd at all. You only think you know, as a matter of fact. And most of your actions are based on incomplete knowledge and you really don’t know what it is all about, or what the purpose of the world is, or know a great deal of other things. It is possible to live and not know.”

As a last thought, there actually has been discussion that the laws of physics can change with time and space – the idea being that the way the laws change can be described by some other more fundamental law. This isn’t a popular view in physics, but that doesn’t mean it’s wrong – it’s entirely plausible.

2. As to your latter question – how do we know quantum mechanics is correct – once again the answer is that we don’t. This one should be slightly more satisfying than the last though.

First, the point must be made that more than any other scientific model, quantum mechanics is very much a match-with-observation theory. There are many physicists out there that think that although it predicts many things correctly, it may not be the fundamental underlying process; it matches observation, but how do we know there isn’t something else going on we aren’t seeing? In fact I’d claim it’s the single-most doubted theory in all of science given the mountain of evidence we have supporting it.

Which leads us to the evidence discussion. There’s a mountain of evidence behind quantum theory but it all follows the same idea as the following example:
Once there was this guy called Schrodinger. People challenged him to find an equation for this new idea he had. He went away on vacation with his wife and came back with some equation. Google it if you want (Schrodinger wave equation). Nobody knew how he came up with it, and he never told. It has imaginary numbers in it – something that people thought was insane at the time. All in all, it’s a pretty sketchy equation. But lo and behold, they went and solved it (oversimplification) and got predictions about where electrons should reside in atoms (for physicists out there, you know I’m kind of forcing this one but spherical harmonics can be derived from the schrodinger equation as well). But remember, it’s quantum mechanics, so you don’t get a definite answer. Rather, you get probabilities and clouds. In order to compare with empirical evidence, the best you can do is record how frequently you get a result and see if it makes sense in the context of your cloud. If you’ve studied statistics, it’s like performing a test to see if you are pulling from the distribution you think you are pulling from. The result was extremely strong agreement between quantum theory and reality. So do we think quantum theory is right? Meh, not necessarily. We know the universe might be doing something else underneath the hood, but whatever it’s doing, it mimics this other thing we found extremely closely, so why not go with our best guess, right? That’s science, just our best guess. (As for other evidence, there are mountains of it, but it all follows the same scheme; you pull results from a distribution and do statistical tests to see if things are in fact what you thought they were)

BRINGING IT BACK – your original question has to do with the many-worlds-interpretation of quantum mechanics. How can we talk about the state of the universe as a cloud if we can only experience one part of the cloud? Well, we came up with a mathematical idea. It fit with reality so we kept it. The consequences of the theory predicted something we cannot possibly test. So do you believe it? Don’t believe that it’s true – believe that it’s plausible. Like Feynman said, you can live and not know. It’s possible to live and not know.

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Profile photo of Eric Eric M (@blankey) 1 year, 11 months ago ago

@tayrex, Ah another Quantum Mechanics buff who is also a hippie, :)

Welcome!

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Profile photo of hazzzdaboss hazzzdaboss (@hazzzdaboss) 1 year, 11 months ago ago

ballin thread. i always feel as if i don’t know enough to contribute… but then i think “who knows enough?”… then i get lost in my head and i don’t contribute… andddd thats my contribution to the thread haha.

@tayrex i dig your persona.

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Profile photo of Tine Tine (@tine) 1 year, 11 months ago ago

@tayrex,

–which says that every point in space is subject to the same laws as every other point in space.–

what comes to mind is an ant, scurrying about his day, the ant represents us, the ant is limited to its perspective, its accumulation of knowledge and experience, on this particular day, a human comes and crushes half of it’s food scavenging group, the human represents a cosmic force, and this greatly impacts the ant colony’s food supply,

how does the ant understand what just happened? bc all it knows it is limited to its day in, day out simplicity, it does not even know what a human is, let alone the massive object that landed upon his work mates, so how would it piece together the situation?

the only thing it knows is that, somehow, something happened, and bc it is limited in what it can know, no matter how much it applies the logic of what it knows to the situation, it will never be able to comprehend what truly happened,

so i argue how much relevance can be placed on observation based upon cause/effect seen here, there probably are laws to the universe, but they are so massive and beyond our world that to use what we know to understand them is equivalent to the ant using what it knows to understand the human terrorist attack….

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Profile photo of Tine Tine (@tine) 1 year, 11 months ago ago

@tayrex,

to a laymen like me, its seems that to understand the forces of the universe we should start with the most obvious, the macro, the force that holds planets in position, gravity, god’s penile gland, however-it-is-labelled, and perhaps there is that i am unaware of, but an understanding of the cosmos will come from an understanding of the framework that holds it together,

are there any quantum theories on this subject? the micro perspective on the macro

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Profile photo of  Anonymous (@) 1 year, 11 months ago ago

This is NOT a remark on this thread in particular. I’m just so tired of the nonsense I’ve seen on this site and the rest of the internet.

“References to quantum mechanics are particularly popular among peddlers of pseudo-scientific claptrap. Quantum mechanics is widely supposed to make weird claims, and hardly anyone understands it, so if you start spouting references to it in support of your own bizarre teachings, people will assume you must be very clever and probably won’t realize that you are, in fact, just bullshitting. So perhaps, if you’re feeling ambitious, put on another seminar entitled “Positive Attitudinal Energies And Quantum Mechanics”.

– Stephen Law

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Profile photo of stonerphysicist stonerphysicist (@tayrex) 1 year, 11 months ago ago

@dalniente, I’m going to disagree with you here. As a scientist, you’ve read this thread with an understanding of quantum mechanics, and that means you’ve noticed places where we may have gone astray. You see where the analogy breaks down. You read a sentence and think to yourself “That’s not quite right” but you decide it’s more trouble than it’s worth to point out.

Now, I’m going to say you need to take a chill pill, because what you think is the motivation behind talking about Quantum Mechanics on an internet forum isn’t what we think is the motivation behind talking about Quantum Mechanics on an internet forum. The goal isn’t to somehow reduce an immensely complicated theory to a few neat sound-bites so that any old layperson can grasp the physics. Rather, concede that such a reduction is impossible, and see that the point of something like this is just to give nonscientists a taste of what we know and love. In fact, I’m going to go so far as to say that sticklers who demand an absolutely formal derivation of physics even when talking to laypeople, are in fact the reason science is so unpopular in this day and age. Quite often I find myself sharing some fascinating part of physics with a nonscientist, and I hear them ask “Is it kind of like…” and proceed to give a not-quite right analysis of the situation which stems from their lack of mathematical or physical understanding. BUT, I stop myself here. Instead of proceeding to point out their misconception and explain the underlying math or physics, which I know will only lead to their eyes glazing over as they slowly tune me out, I tell them “it’s kind of like that”. I say that there’s some complicated math that they don’t need to know, and that they should stick to what I’ve told them and try not to go too far off the deep end. If we want people to at all humor us in our bizarre investigations into the world, we need to not overwhelm them. We need to straddle the tiny line between misunderstanding and simplification, so that everyone gets the most out of our knowledge.

Finally, as this pertains to the perception of the speaker when it comes to sharing knowledge, let me tell you a story about a math teacher I had in high school. He won best teacher of the year in our state. He could teach the pants off of math, but understood very little himself. I realized this senior year when we were asked to do an external investigation and it became apparent we were equals in the world of math: he wasn’t a math god, he just knew how to convey the ideas very effectively. You would have me disregard his teachings for his depth of understanding was very little when compared to a true mathematician. BUT do you really think I would have benefited more from having it taught formally by somebody who stayed true to the rigor of true math instead of having it dumbed down for me? (Well, perhaps, but that’s a question for our math education people to decide in the future)

All I know is that there’s nothing wrong with explanations that sacrifice rigor and reasoning if they are capable of getting the student interested enough in the subject to later come back and fill in the gaps in their knowledge – a complete understanding is only a necessary component if you plan to create new knowledge based on your current knowledge – which by definition is NOT a layperson’s role.

All that said, I see where you’re coming from and I know it’s a little infuriating, but I’ll take when I can get when it comes to sharing the wonder of quantum mechanics via text on an internet forum.

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